Production of alkyl aromatic sulfonic acids and the alkylate therefor



United States Patent Office 2,718,526 Patented Sept. 20, 1955 PRODUCTION OF ALKYL AROMATIC SULFONIC ACIDS AND THE ALKYLATE THEREFOR No Drawing. Application November 23, 1951,

- Serial No. 257,956

13 Claims. (Cl. 260-505) This application is a continuation-in-part of my copending application Serial No. 50,004, filed September 18, 1948, now abandoned.

This invention provides an improved, economical process for the alkylation of aromatic hydrocarbons and for the conversion of the resulting alkylate to the corresponding sulfonic acid and sulfonate salt derivatives thereof. More particularly, the invention concerns a method of producing alkyl aromatic sulfonic acids useful as detergent intermediates by an economical process whereby the recovered, partially spent sulfonating reagent utilized to convert previously formed alkylate to the corresponding sulfonic acid is employed as the alkylation catalyst in the reaction for forming said alkylate.

The basic process for manufacturing synthetic detergents of the alkyl aromatic sulfonate type comprises a series of reaction stages in which an alkyl aromatic hydrocarbon of specific structure, generally formed in a preliminary stage of the process, is subjected to sulfonation to form the corresponding mono-sulfonated derivative which may then be, and is preferably, neutralized with a suitable basic reagent, such as caustic alkali, to convert the resulting sulfonic acid to the corresponding sulfonate salt. The salt formed on neutralizing the alkyl aromatic sulfonic acid is actively detersive in an aqueous solution thereof, but is desirably composited with certain so called builder salts prior to its use, the presence of which tend to enhance its detersive activity.

The alkyl aromatic hydrocarbons of specific structure desired for detergent production and comprising the charging stock to the subsequent sulfonation stage of the process are not normally found occurring in natural sources such as petroleum distillate fractions and must therefore be obtained by synthesis from other primary sources. The present invention concerns a method for producing such detergents by a combination alkylation-sulfonation process in which the sulfonating reagent utilized in the sulfonation stage of the process, and as recovered therefrom, is utilized as the catalyst in the synthesis of the alkyl aromatic hydrocarbon intermediate.

The combination alkylation-sulfonation process herein provided may be applied with particular advantage to those alkyl aromatic hydrocarbons containing a monocyclic nucleus, that is the alkyl benzenoid derivatives, although useful detergents may also be prepared from the alkylated polycyclic hydrocarbons such as the alkyl naphthalenes, phenanthrenes and anthracenes. Especially desirable detergents have been prepared from the alkyl benzenoid hydrocarbons containing one alkyl group having from about 9 to about 18 carbon atoms, preferably from about 11 to about 13 carbon atoms and, in addition, 1 or 2 other short chain alkyl groups containing not more than 2 carbon atoms per group. The preferred alkylates as formed in the present alkylation procedure contain a benzenoid nucleus, an alkyl group containing from about 11 to about 13 carbon atoms per group and a single short chain alkyl group, preferably the methyl radical.

In the production of the alkyl aromatic hydrocarbon intermediate containing the preferred benzenoid nucleus, an aromatic hydrocarbon such as benzene, toluene, xylene, methylethylbenzene or diethylbenzene, preferably benzene or toluene, is condensed or alkylated with an alkylating agent comprising an olefinic hydrocarbon containing from about 9 to about 18 carbon atoms per molecule. The preferred olefinic hydrocarbons utilized as alkylating agents in the formation of the present alkyl aromatic hydrocarbon are those fractions containing components of relatively straight chain hydrocarbons produced, for example, by the polymerization of lower molecular weight olefins such as propylene and/or butylene or derived from suitably boiling fractions recovered from thermally cracked petroleum products such as a pressure I distillate fraction thereof.

and reagents for enhancing the yield and quality of theultimate detergent product at greater economy than is normally achieved in the absence of the features provided herein. The present flow involves the use of a sulfuric acid oleum as sulfonating agent for converting alkyl aromatic hydrocarbons formed in a prior reaction cycle to their sulfonic acid derivatives, separating from the products of the sulfonation reaction a phase comprising predominantly sulfuric acid containing not more than about 10% by weight of water and utilizing the latter sulfuric acid phase as catalyst in an alkylation reaction for the production of said alkyl aromatic hydrocarbons.

The sulfonation reaction is preferably effected in the presence of a suitable non-reactive solvent or diluent which enhances phase separation between the alkyl aromatic sulfonic acid product and residual excess sulfonating agent, which in the case of some charging stocks is effected only with difficulty or only after additional special treatment of the reaction mixture to effect phase separation.

(above about 95%) within a reasonable time and, further-- more, form detergents of excellent quality. The presence of the above specified diluent or solvent in the sulfonation reaction mixture is considered advantageous when a sulfonating agent comprising an oleum containing at least 15% free sulfur trioxide is utilized as a sulfonating agent and when products of high detergency are to be obtained from the reaction mixture. In the absence of said diluent and when oleums of high concentrations are employed (such as 65% oleum), the ratio of sulfonating agent to charging stock required is much higher (approximately 4 mols of total S03 per mole of hydrocarbons as compared to l to 1.8 mols per mol of hydrocarbon charging stock when said diluent is present) and the product possesses undesirable color and a lower detergency than the product formed in the presence of said diluent.

The partially spent sulfonating agent recovered from the sulfonation reaction mixture in the present process is of at least concentration, based only upon the amount of sulfuric acid and water and excluding organic material which may be present therein, and is of sufiicient activity as an alkylation catalyst to effect condensation of an olefinic alkylating agent and an aromatic hydrocarbon at the alkylation conditions herein specified to form the present alkyl aromatic charging stock to the sulfonation stage of the present process. The used sulfuric acid oleum phase recovered from the sulfonation products desirably contains from about 95 to about 100% sulfuric acid (that is, not more than about 5% by weight of water), and the most desirable acid from the standpoint of effectiveness for catalyzing the alkylation reaction contains approximately 98.5% sulfuric acid or not more than about 2.5% water. The used sulfonating'agent will contain sulfuric acid of at least 95% concentration when the originaloleum employed in the sulfonation stage contains at least 50% free sulfur trioxide or when the amount'of oleum charged is greater than about 1.6 to about 3 mols of total sulfur trioxides per mol of'hydrocarbon alkylate.

In the use of oleums containing less than 50% free sulfur trioxide, the quantity of oleum utilized in the sulfonation reactionmust generally be greater than about 3 mols of total S03 per mol of hydrocarbon alkylate in order to attain-95% sulfonation and the recovered spent sulfonating agent phase will contain sulfuric acid of at least 95% concentration (based on a'water-content of not more than 5% by weight of the acid) for utilization in the alkylation reaction as catalyst therefor. Thus, the acidity'of the recovered spent sulfonating agent will ultimately depend not only upon the concentration of the original oleum utilized in the-sulfonationreaction, butalso upon the quantity of oleum'used. These factors must-be mutually determined prior to operation of the process and the requirements vary with variations in the charging stocks. The present invention embodies several alternative procedures for recovering the spent sulfonating acid from the sulfonation reaction mixture and utilization of the same as alkylation catalystin a subsequent reaction for alkylating an aromatic-hydrocarbon with an olefinic alkylating agent; these alternative procedures comprising specific and separate embodiments of the present invention. In accordance with one of its embodiments this invention concerns an alkylation reaction in combination with a sulfonation reaction-for the production of an alkyl aromatic sulfonic acid which comprises alkylating an aromatic hydrocarbon with an olefinic hydrocarbon containing from about 9 to about 18 carbon'atoms per molecule in the presence of an alkylation catalyst comprising sulfuric acid containing from 0% to about 10% by'weight of water and comprising essentially used sulfonation acid recovered from the product of a prior sulfonation reaction, separating an alkyl aromatic hydrocarbon from the resulting alkylation product, reacting said alkyl'aromatic hydrocarbon with'a sulfonating agent comprising a sulfuric acid oleum, separating used sulfonating agent'comprising predominantly sulfuric acid from theproduct-of the sulfonation reaction, adjusting the water content of said used sulfonating agent to containtherein sulfuric acid of from about 0% to about 10% byweight of water and utilizing the resulting used snlfuricacidas catalyst in the aforesaid alkylation reaction to form saidalkyl aromatic hydrocarbon.

A more specific embodiment of the presentinvention relates we process comprising an alkylation'reaction in combination with a sulfonation reaction for the-production ofan-alkylaromatic sulfonic acidwhich comprises alkylating an aromatic hydrocarbon with an ole'finic hydrocarbon containing from about '9 to about 18 carbon atoms per molecule 'in the presence of an alkylation catalyst comprising sulfuric acid containing from 0% to about 10% by weight of water, said sulfuric acid comprisingthe used acid phase separated from the product of a prior sulfonation reaction as hereinafter formed, separating the alkyl aromatic hydrocarbon from the resulting alkylation reaction product, reacting said alkyl aromatic hydrocarbon with a sulfuric acid oleum containing at least free sulfur trioxide at sulfonating conditions-to effect sulfonation'of said alkyl aromatic hydrocarbon, adding an amount of water-to the resulting sulfonation reaction mixture sufficient to causethe separation therefrom of a used sulfuric acid phase, adjusting the water content of said sulfuric acid phase to contain from 0% to about 10% by weight of water, and utilizing the resulting sulfuric acid as catalyst in the aforesaid alkylation reaction to form said alkyl aromatic hydrocarbon product.

Another specific embodiment of the present invention relates to a process comprising an alkylation reaction in combination with a sulfonation reaction for the production of an'alkyl aromatic sulfonic acid which comprises alkylating an aromatic hydrocarbon with an olefinic hydrocarbon containing from about 9 to about 18 carbon atoms per molecule in the presence of an alkylation catalyst comprising sulfuric acid containing from 0% to about 10% by weight of water, said sulfuric acid comprising the used acid phase separated from the product of a prior sulfonation reaction as hereinafter formed, separating an alkyl aromatic hydrocarbon from the resulting alkylation reaction product, admixing said alkyl aromatic hydrocarbon with an inert diluent selected from the paraflinic and naphthenic hydrocarbons and their halogenated analogs, contacting said mixture with a sulfuric acid oleum in an amount sufiicient to effect substantial sulfonation of said alkyl aromatic hydrocarbon, permitting a usedsulfuric acid oleum phase to stratify from the reaction mixture on standing, separating said oleum phase from the reaction mixture, adjusting-the water content of said used sulfonating agent to contain from 0% to about 10% by weight of water and utilizing the resulting sulfuric acid as catalyst in the aforesaid alkylation reaction to form said alkyl aromatic hydrocarbon.

Observations have shown that in the sulfonation of alkyl aromatic hydrocarbons With a'sulfuric acid oleum, particularly an oleum containing at least 15% free sulfur trioxide, a relatively homogeneous reaction mixture results, under certain conditions, comprising an emulsion of unsulfonated hydrocarbons (if any), and excess oleum and sulfonic acids which does not readily separate into distinct phases or strata on standing, unless an inert hydrocarbon or halogenated diluent is present in the reaction mixture during or after the sulfonation reaction. The difficultly'separated emulsion which forms in the absence of an inert diluent will, however, separate into two distinct separable phases one of which comprises predominantly the sulfonic acid product and the other used or excess sulfonating agent by the addition of sufficient water to the reaction mixture to break the emulsion. The amount of water required to break the emulsion, or spring the sulfonic acid from the reaction mixture varies with the particular charging stock undergoing sulfonation, the temperature of the reaction mixture and the concentration and amount of the oleum sulfonating agent. 'Phase separation takes place with a majority of alkyl aromatic hydrocarbon charging stocks when the concentration of the used oleum or sulfuric acid phase which separates from the reaction mixture is above concentration of sulfuric acid, herein preferred for subsequent use in the alkylation stage of the process. In

-many cases, especially when the quantity of oleum charged to the sulfonation reaction is greater than 3 mols. of total 503 per mol of hydrocarbon charging stock or when the concentration of sulfur trioxide in the oleum is'considerably abovethe 15 minimum preferred herein, the used sulfuric acidphase may contain free sulfur ,trioxide when phase-separation takes place, if water addition is not required to effect phase separation. When the sulfonation diluent-is utilized in the sulfonation reactor, the sulfonic acid product preferentially dissolves sired-90 to sulfuric acid prior to its use in the alkylation Stage of the process or'the'dilution may be-etfected while in admixture with the other component of the sulfonation reaction mixture.

The preferred sulfonating agent utilizable in the present process is designated as an oleum, that is, 100% sulfuric acid containing dissolved free sulfur trioxide not combined with water as sulfuric acid. Particularly desirable oleums for this purpose contain at least 15% free sulfur trioxide which theoretically provide a minimum of 1.0 plus 0.216 or 1.216 mols of total sulfur trioxide per mol of actual sulfuric acid contained in the sulfonating agent. In actual operation however, only the free sulfur trioxide component of the sulfonating agent is removed therefrom during the initial stages of the sulfonation reaction, such that the remaining sulfonating agent becomes progressively weaker in free sulfur trioxide content and simultaneously weaker as a sulfonating agent until the concentration approaches that of 100% sulfuric acid when sulfonation becomes relatively sluggish at the sulfonation conditions provided in the present process. When the reaction approaches this stage or even before the concentration of the oleum is reduced to 100% sulfuric acid, the used sulfonating agent is separated from the reaction mixture and reserved for subsequent use in the alkylation reaction as catalyst therefor. Since the sulfonating activity of the oleum and the rate of reaction in the last analysis depends upon the concentration of free sulfur trioxide therein, it is desirable for this reason that the sulfonating agent contains as high a percentage of free sulfur trioxide as it is practicable to utilize in the present process, although in some cases, as when utilizing a large volume ratio of 100% sulfuric acid or an oleum containing less than 15% free sulfur trioxide per volume of alkyl aromatic hydrocarbon such latter types of sulfonating agents may likewise be utilized in the sulfonation stage of the present process.

As heretofore indicated, the quantity of oleum or other sulfonating agent required in the sulfonation reaction mixture will ultimately depend upon its concentration, the rate of reaction desired, and the presence or absence of an inert diluent in the reaction mixture. For oleums containing up to 15% free sulfur trioxide, the molar ratio of said oleum to alkyl aromatic hydrocarbon charging stock is desirably maintained at from about 4 to 1 to about to 1 of total sulfur trioxide (combined and free) per mol of hydrocarbon charging stock. For those oleums containing a greater concentration of free sulfur trioxide than ,15 the corresponding ratio of oleum to' alkyl aromatic charging stock is maintained at from about 1 to about 3.5 mols of total sulfur trioxide per mol of charging stock, preferably from about 1.6 to about 3.0 on a, molar basis. The preferred oleums utilizable in the sulfonation stage of the process contain about 65% uncombined sulfur trioxide and the corresponding ratio of oleum to alkyl aromatic hydrocarbon may be as low as about 1.6 to 1. An oleum containing 25% uncombined sulfur trioxide is utilized in conjunction with oleum to hydrocarbon molar ratios as low as 3 to 1. r

p The diluent or inert solvent herein specified for utilization in the sulfonation reaction mixture is more specifically characterized as a normally liquid or liquefiable substance which is essentially inert at the sulfonating conditions employed to effect sulfonation at temperatures in proximity of the sulfonation reaction temperature. Thus, the diluent may be a material which boils normally at a temperature approximately equal to or below the desired sulfonation reaction temperature, or it may be a material which can be induced by suitable pressure regulation to boil at a temperature about equal to or below the desired sulfonation reaction temperature so that in any event it can also be retained in the liquid phase in the sulfonation reaction mixture by suitable regulation of the pressure in thesulfonation reactor. The preferred diluents are the inert parafiinic hydrocarbons containing at least 3 carbon atoms per molecule and preferably not more than about 8 carbon atoms per molecule, such as liquefied propane,

normal butane, n-pentane and homologs, or mixtures thereof which boil at such temperature and pressure conditions that said hydrocarbons provide evaporative cooling at the sulfonation reaction conditions. Non-reactive cycloparaflins, i. e., those of the cyclopentane or cyclohexane series boiling in the same range, may also be utilized herein. Another class of compounds suitable as inert diluents include the monoor polyhalogenated hydrocarbons containing not more than 8 carbon atoms per molecule such as the fluorinated, chlorinated and/or brominated hydrocarbons, represented, for example, by such compounds as trichloroethane, hexachlorocyclohexane, Freon (dichlorodifluoromethane) or a halogenated hydrocarbon wherein all of the halogen atoms of the hydrocarbon analog are replaced by halogen atoms, including such compounds as the halocarbons, represented, for example, by carbon tetrachloride perfluoropropane and perfluorobutane.

An especially desirable inert diluent for use with 5065% oleum is normal butane and/ or propane which boils at temperatures of from about 15 to about 0 C. at atmospheric pressure. These diluents may be readily stripped from the sulfonation reaction mixture following the completion of the sulfonation reaction and are readily recoverable therefrom by pumping the vapors from the stripping operation into a condenser operated at a pressure in excess of the vapor pressure of the diluent at the sulfonation temperature.

In the alkylation stage of the present process an aromatic hydrocarbon, as for example, benzene or toluone, the preferred aromatic charging stocks herein, is alkylated with an olefinic hydrocarbon containing from about 9 to about 18 carbon atoms per molecule, preferably from about 11 to about 13 carbon atoms, the reaction being effected in the presence of the recovered, used sulfonating agent phase of the prior sulfonation reaction in which the water content has been adjusted to provide an acid containing from about to about 100% organicfree sulfuric acid, preferably from about to about 98% of said sulfuric acid. The use of the recovered sulfonation acid as alkylation catalyst tends to reduce the amount of undesirable sulfonation of the aromatic hydrocarbon reactant and polymerization of the olefinic reactant utilized in the alkylation reaction, which normally occur during alkylation when utilizing fresh sulfuric acid of comparable concentration as alkylation catalyst. This advantageous effect is essentially due to the presence of organic material in the used sulfonation acid dissolved and/or entrained therein from the sulfonation reaction mixture, the organic material present in the used sulfonation acid tending to inhibit or deter further sulfonation and polymerization of the aromatic and olefinic alkylation reactants. The reaction is preferably effected at temperatures of from about 10 to about 50 0., preferably from about 0 C. to about 30 C. The molar ratio of aromatic hydrocarbon to olefinic hydrocarbon alkylating agent charged to the alkylation reaction is desirably maintained at a value greater than 1, preferably from about 1 to about 10, although this factor may be varied with considerable latitude to obtain desired effects thereby. During the course of the alkylation, until the reaction approached equilibrium conditions, the reaction mixture, comprising hydrocarbons and sulfuric acid alkylation catalyst, is desirably stirred in order to maintain intimate contact between the catalyst and hydrocarbon phases. Upon completion of the reaction, the resulting mixture is allowed to stand quiescent until the respective catalyst and hydrocarbon phases have stratified into an upper hydrocarbon phase containing the alkyl aromatic hydrocarbon product, unreacted aromatic and olefinic hydrocarbon reactants, and a lower spent sulfuric acid catalyst phase which may be withdrawn from the reaction mixture. The

upper hydrocarbon phase may then be washed and frac-' tionated to separate therefrom a suitable fraction comprising the alkyl aromatic hydrocarbon product desired for the subsequent sulfonation stage. .In the case of toluene alhylate,.for example, the desired fraction fordetergent production therefrom boils from .about 275 to about 3.45 ..C..and contains ,alkyl aromatic hydrocarbons having a single long chain alkyl group containing from about .11 to about 13 carbon atoms per group.

The operatingconditions maintained in the sulfonating reactor .are determined by the type of alkyl aromatic compound .undergoing sulfonation, and the particular oleum used. For .most of said alkylate hydrocarbons, and especially in the case of the alkyl benzenoid charging stocks, the .sulfonation temperature is desirably maintained at from. about 20 to about +50 C., preferably at temperatures of from about 10 to about C. for 50 60% oleums or to +35 C. for l550% oleums,.the ambient pressure above the sulfonation reactionmixture being maintainedduring sulfonation at a value sufiicient to provide substantially liquid phase conditions in the reaction mixture. In the presence of a diluent, .however, the pressure is .desirably adjusted to allow .at least a portion of the liquid inert diluent to evaporate andprovide evaporative cooling when the temperature of the sulfonation reaction mixture tends to exceed the desired value. In the case of butane for example, the sulfonation reaction may be operated at substantially atmospheric pressure when the sulfonation temperature is maintained at about 0 C. Reaction periods of from about 5 to about 45 minutes are generally sufficientto effectsubstantially complete sulfonation of the alkylate charge, the preferred time of reaction being from about to about minutes. The volume ratio of liquid inert diluent to alkylate charging stock maintained in the sulfonation reactor during the sulfonation reaction depends somewhat on the particular diluent and, in general, is maintained Within the range of from about 1 to 1 to aboutyS to 1 when hydrocarbons are employed as the diluent.

The present process may be operated as either a batch or continuous type of operation, although the continuous method of producingthe present alkyl aromatic sulfonic acids is generally preferred. In a typical continuous method, the aromatic charging stock is mixed with the olefinic hydrocarbon alkylating agent and the mixture charged to an alkylation reactor containingthe previously separated spent sulfonating agent containing sulfuric acid of from about 90 toabout 100% concentration and maintained therein at fromabout 10 to about 20 C. to effect alkylation. The mixture ,of .alkylation catalyst and hydrocarbons is stirred or otherwise agitated until alkylation has taken place and the mixture is thereafter allowed tosettleto separate asubstantially hydrocarbon phase. froma lower spent sulfuric acid alkylation catalyst phase. The latter spent acid phase is withdrawn while the retained-upper hydrocarbon phase isfurther treated, for example by washing and drying, and removed to a fractional distillation apparatus to separate the alkyl aromatic hydrocarbon fraction therefrom desired for detergent production. The alkylate fraction is thereafter mixedwith the desired proportion of the inert diluent herein specified, brought to the desired sulfonation reaction temperature, and thereafter contacted with oleum of the-above specified concentration to effect sulfonation, the components being-mixed as a flowing stream to the sulfonation reactor to provide continuous operation. During the course of the reaction, the mixture is agitated withthe aid of a stirring device to obtain desirable intimatecontact between the reactants and diluent charged tothe process. When the reaction approaches equilibrium, usually within -a time period of from about 5 to about 60 minutes,the mixture may be diluted with water toa separatedsulfuric acid strength suitable for use as an alkylation catalyst and transferred .to a settling vessel where the usedsulfonating agent is withdrawn for usein azsubsequent .alkylation reaction .as catalyst therein. The sulfoniclacid-butane mixture is then transferred into a suitable stripping tower operated at relatively higher temperatures and/or lower pressures than the sulfonation reactor in order to'strip the diluentfrom the remaining components of the reaction mixture. In order to facilitate the separation of the used sulfuric acid phase, it maybe desirable to add water to the sulfonation reaction mixture in sufficient quantity to spring the sulfonic acid phase therefrom and then allow the mixture to stratify until phase separation takes place. The amount of water is sufficient to provide a sulfuric acid phase containing an acid of from about to about concentration for subsequent utilization in the alkylation stage of the process. The upper sulfonic acid phase separated from the sulfonationreactiou mixture may be directly neutralized with a suitable caustic solution such as an aqueous ,solution ofsodium or potassium hydroxide, an aqueous amine, alkanol amine, or other basic neutralizing agent to form the corresponding salt of the alkyl' aromatic .sulfonic'acids. The resulting aqueous solution may then be composited with a suitable builder salt such as. sodium sulfate, sodium metasilicate, a sodium phosphate or other salt selected for this purpose in the desired proportion to form an aqueous solution or slurry which upon drying will yield the desired detergent composition.

In thus specifying the preferred reagents and general method of procedure in the aforementioned description, it is not intended thereby to limit the scope of the present invention ,in strict accordance thereto and other means Within reasonable contemplation of the present disclosure and the skill of the art are to be considered within the present process flow. Thus, for example,.although oleums of greater than 15% free sulfur trioxide content are preferred as sulfonating agents, oleumsof lesser concentration as well as 100% sulfuric acid are also utilizable herein with modifications of the procedure described for the use of said preferred oleums.

The process of this invention is further illustrated in the following example which describes the present process in accordance with specific embodiments of the invention. The example, however, is not to be construed as limiting the invention in any of its broad aspects.

Two sulfuric acid catalyzed alkylation reactions were conducted under as nearly comparable conditionsas possible tocompare the use of fresh sulfuric acid alkylation catalyst with used sulfonation acid as catalyst. In one of the runs fresh sulfuric acid containing 97.5% sulfuric acid and 2.5% water was utilized as the alkylation catalyst and -in the other experiment, sulfuric acid containing 2.4% water and of 92.2% total acidity, being the acid phase recovered'from a prior sulfonation reaction ,mixture in which dodecyltoluene was sulfonated with 24.5% oleum, was utilized as the alkylation catalyst. Accordingly, the sulfuric acid employed in the present experiment was prepared by sulfonating a .dodecyltoluene fraction (the alkylate; product formed by condensing toluene with a propylene tetramer fraction boiling from to 225 C.) with 24.5% oleum and controllingthe sulfonation temperature to Within the range of from -1 to +2 C. with the aid of refluxing-liquid n-butanepresent in the reaction mixture. For this purpose, one liter (87.2 grams or 3.35 moles) .of dodecyltoluene and 1.5 liters of liquid butane were mixed and thereafter cooled by the refluxing butane to a temperature-of about -1 .C. A total of 2190 grams of oleum containing seven moles of free and combined sulfur trioxide was added to the cooled dodecyltoluene-butane mixture over a period of 1.5 hours as the reaction mixture was vigorouslystirred in the flask. Following the addition of theabove quantity of oleum, the .mixture was stirred for anadditional two hours and thereafter mixed with fifty-five grarnsof water, while maintaining the reaction mixture within the above temperature range. A three-layer system formed after the addition of water and allowing the mixture to stand .quiescent for several minutes: (,1) an upper layer comprising essentially butane and ,unsulfonated alkylate, (2) a middle layer comprising dodecyltoluene sulfonic acid, a smallamount of dissolved butane and a small quantity of sulfuric acid, and (3) a lowermost layer comprising 1437 grams of spent sulfonation acid containing 2.4% water, and having a total acidity of 92.2%, including a quantity of dissolved sulfonic acids. The lowermost layer comprising the spent sulfonation acid was separated by decantation from the upper layers and reserved for use in the following alkylation reaction as the sulfuric acid alkylation catalyst therein.

In each of the following alkylation runs wherein the use of the above-prepared spent sulfonation acid is compared with a fresh 97.5% sulfuric acid as alkylation catalyst for the condensation of toluene with a propylene tetramer fraction boiling from 170 to 225 C.', a toluene concentrate containing 56% by weight of toluene, the balance of which consisted of n-heptane, was mixed with the propylene tetramer fraction in a molar ratio of toluene to tetramer of 1.5 to 1 and the resulting hydrocarbon mixture introduced into an alkylation reaction flask simultaneously with the sulfuric acid alkylation catalyst. The contents of the alkylation flask were maintained at a temperature of 35 C.-3 C. by cooling the flask in a salt-ice bath. The acid and hydrocarbon mixture were run into the alkylation flask over a period of 1.5 hours, following which the mixture of acid catalyst and hydrocarbons was stirred for an additional 1.5 hours. ,The alkylation reaction mixture following the above total time of three hours was allowed to separate into two layers, an upper essentially hydrocarbon layer and a lower spent sulfuric acid alkylation catalyst layer, the latter being withdrawn from the upper layer by decantation. The recovered hydrocarbon mixture was thereafter washed with water to remove entrained acid, dried over anhydrous sodium sulfate and fractionally distilled. The alkylation reaction conditions utilized in the experiment and the results of these comparative experiments are reported in the following Table I, providing a ready basis of comparison between the two runs.

Table I Alkylation Catalyst Fresh Used H2804,

H1804 Containing Coutain- 2.4% Water, ing 2.5% Separated Water from Sulfonation Reaction Mixture Amount of Catalyst Charged 1 732 1 714 Hydrocarbons Charged:

Propylene tetramer (170-225 C., B. P.),

gr 376 376 Toluene (as concentrate), gr 1 552 1 552 Total Hydrocarbon, gr 928 928 .Ar- ,Oleiin, moles 1. 5/1 1. 5/1 Recovery of Products:

Total Hydrocarbon, upper layer, gr-.." 832 857 Total Acid, lower layer, gr 883 771 Hydrocarbon Analysis, by distillation:

Toluene Concentrate fraction, gr 271 309 Toluene, recovered, gr 21.1 57. 5 Alkylate, B. P. 275345 0., fraction, gr 489 498 Conclusions:

Toluene consumed, mols. toluene/mole a1 late 1. 665 1. 427 Alkylate produced, lbs. alkylate/lb. of

olefin 1. 30 1.323

1 Grams (400 ml.). 2 309 gr. toluene.

It is evident from the results obtained in the above comparative runs that even though the used sulfuric acid contained less total acidity (92.2% as compared to 97.5%) than the fresh sulfuric acid utilized in the comparative run, and thus might be expected to yield less alkylate product, the alkylation efiected with the used sulfonation acid as catalyst produced a greater alkylate yield per pound of olefinic tetramer charged to the alkylation reaction than the use of fresh acid (1.323 compared to 1.30) and the quantity of toluene consumed in 10 the alkylation was substantially less in the case of utilizing spent sulfonation acid catalyst than in the case of using fresh sulfuric acid as the alkylation catalyst (1.427 as compared to 1.665 moles of toluene consumed per mole of alkylate produced). The disparity in toluene consumption'between the two runs appears even more pronounced and the advantages of employing the used sulfonation acid as alkylation catalyst is more marked when consideration is given to the fact that less toluene is consumed in the used acid run to produce a greater yield of the desired alkylate than in the fresh acid run. Although the reduced toluene consumption utilizing the sulfuric acid catalyst recovered from the prior sulfona tion process is a relatively small numerical value when expressed on a molar basis (i. e., 0.238), the saving in toluene when expressed on a percentage basis is 8.42% based on the alkylate produced, thus indicating the substantial economic advantages of the improved procedure of this invention, not only from the standpoint of the saving in toluene consumed, 'but also the saving in consumption of acid required as catalyst for effecting the condensation to form the alkylate.

I claim as my invention: 1 1. A process Which comprises alkylating an aromatic hydrocarbon with an olefinic hydrocarbon of from about 9 to about 18 carbon atoms per molecule in the presence of a sulfuric acid alkylation catalyst, sulfonating the resultant alkylated aromatic hydrocarbon with sulfuric acid oleum, and supplying used oleum from the sulfonating step to the alkylating step to constitute at least a part of said alkylation catalyst.

2. A process comprising an alkylation reaction in combination with a sulfonation reaction for the production of an alkyl aromatic sulfonic acid which comprises alkylating an aromatic hydrocarbon with an olefinic hydrocarbon containing from about 9 to about 18 carbon atoms per molecule in the presence of an alkylation catalyst comprising sulfuric acid containing from 0% to about 10% by weight of water and comprising essentially used sulfonation acid recovered from the product of a prior sulfonation reaction, separating an alkyl aromatic hydrocarbon from the resulting alkylation reaction product, reacting said alkyl aromatic hydrocarbon with a sulfuric acid oleum sulfonating agent, separating used oleum from the resulting sulfonation reaction product, adjusting the water content of said oleum to contain from 0% to about 10% by weight of water, and utilizing the resulting acid as catalyst in the aforesaid alkylation reaction to form said alkyl aromatic hydrocarbon.

3. The process of claim 1 further characterized in that said aromatic hydrocarbon is a benzenoid aromatic hydrocarbon.

4. The process of claim 1 further characterized in that said aromatic hydrocarbon is toluene.

5. The process of claim 1 further characterized in that said olefinic hydrocarbon is a proplyene polymer having a boiling point of from about to about 225 C.

6. The process of claim 1 further characterized in that the concentration of sulfuric acid in the used sulfonating agent employed as alkylation catalyst is adjusted to contain from 0% to about 5% by weight of water.

7. The process of claim 1 further characterized in that said oleum contains at least 15% free sulfur trioxide.

8. The process of claim 1 further characterized in that said sulfuric acid oleum contains at least 60% free sulfur trioxide.

9. The process of claim 1 further characterized in that said oleum contains up to 15% free sulfur trioxide and the oleum to alkyl aromatic hydrocarbon molar ratio charged to the sulfonation reaction is from about 4 to l to about 10 to 1, where said oleum molar ratio is based upon the total sulfur trioxide content of said oleum combined as sulfuric acid and as free sulfur trioxide.

.10. The process of .claim 1 .further characterized in thatgsaidoleum contains atleast 15% :freesulfurrtrioxide and the oleum to ialkylate hydrocarbon molar ratio chargcdutothe sulfonation reactionjs from about v1 to 1 to about 3.5 to 1, where said oleum molar ratio is based upon the total sulfur rtrioxide content of saidoleum as combined .sulfuricvacid and free sulfur-trioxide.

.11.sA,process comprising .an alkylation reaction in combination with a. sulfonation reaction .for 'the .produc-t tion of an .allgylaromatic sulfonicacid which comprises alkylatiug anaromatic hydrocarbon with an .ole'finic hydrocarbonfcontainingfrom about 9 to about ,18 carbon atoms per molecule in the presence of an ,.alkylation catalyst comprising sulfuric acid containing from 0% to about 0% by weight of water-and comprising essentially used sulfuric acid recovered from theproduct of aprior sulfonation reaction, separating an alkyl aromatichydrocarbon from the resulting alkylation reaction product, reacting saidallgyl aromatichydrocarbon with a sulfuric acid oleumr at sulfonating conditions to eifect sulfonation of .said hydrocarbon, adding an amountof Water to the resulting sulfonation'reaction mixture sufficient to cause the separation therefrom of a used sulfuric acid phase, adjusting the water content of said sulfuric acid phase to contain from 0% to 10% by weight of water, and utilizing the resulting acid as catalyst in the aforesaid alkylation reaction to form said alkyl aromatic hydrocarbon product.

12. A process comprising an alkylation reaction in combination with a sulfonation reaction for the production of an alkyl varomatic sulfonic acid which comprises alkylating an aromatic hydrocarbon with an olefinic hydrocarbon montaining from about .9 to vabout 18 t carbon atomsper molecule in thepresence ofl anralkylation catalyst.comprising-sulfuric acid containing-from 0% to about 10% by weight of waterand comprising essentially-used sulfuric .acid recovered from a prior. sulfonation I reaction, separating lan alkyl aromatichydrocarbon from theresulting alkylation reaction product, admixing said alkyl aromatic hydrocarbon with .an inert diluent selected from the .paraffinic and ,naphthenic hydrocarbons and .their halogenated-analogs, contacting said mixture with a:sul- .furic .acid .oleum in an amountsufiicient to effect substantial sulfonationof said alkyl aromatic hydrocarbon, permitting a used sulfuric acid oleum phase to stratify from the reaction mixture on standing, scparatingtsaid oleum phase :from the reaction .mixture, adjusting .the water content of said oleum to contain from .0% .toabout 10% by weight of water and utilizing the resulting acid as vcatalyst in the aforesaid tallgylation reaction to .form said alkyl aromatic hydrocarbon.

.13. The process of claim lZQfurther characterized in that said inert diluent is normal butane.

References Cited inthc file 'of-thispatent UNITED STATES PATENTS 2,203,443 Ross June14, 1940 2,244,512 Brandt June 3, 1941 2,456,119 Friedman et a1. Dec. 14, "1948 2,470,896 Mavity May 2A, 19:49 '/2;479,120 'Johnstone Aug. 16, 1949 2,567,854 Nixon Sept. .1 1, 11954 

1. A PROCESS WHICH COMPRISES ALKYLATING AN AROMATIC HYDROCARBON WITH AN OLEFINIC HYDROCARBON OF FROM ABOUT 9 TO ABOUT 18 CARBON ATOMS PER MOLECULE IN THE PRESENCE OF A SULFURIC ACID ALKYLATION CATALYST, SULFONATING THE RESULTANT ALKYLATED AROMATIC HYDROCARBON WITH SULFURIC ACID OLEUM, AND SUPPLYING USED OLEUM FROM THE SULFONATING STEP TO THE ALKYLATING STEP TO CONSTITUTE AT LEAST A PART OF SAID ALKYLATION CATALYST. 